Investigations on pyrazine derivatives II. The preparation of pyrazine 2,3,5‐tricarboxylic acid and of pyrazine 2,5‐ and 2,6‐dicarboxylic acids

A satisfactory preparative method for pyrazine tricarboxylic acid has been found in the oxidation of the readily available 2‐(D‐arabo)‐tetrahydroxybutylquinoxaline. Pyrazine tricarboxylic acid is easily decarboxylated to pyrazine 2,5‐ and 2,6‐dicarboxylic acids. In connection with the poor yield obtained in the oxidation of 2,5‐dimethylpyrazine to pyrazine 2.5‐dicarboxylic acid, it is an advantage first of all to convert the starting material into a condensation product with an appropriate aldehyde.